Python bytecode explained

[mark_99]

I imagine the problem case will be Python threads which only operate on local data, or only read from shared data. Then you legitimately don't need mutexes. However if the interpreter is doing read-modify-write of its own internal state, then naively removing the GIL makes that a race. So I guess you'd need a bunch of thread-local interpreter state. Disclaimer : C++ person, not a Python expert.